1. Field of the Invention
The present invention relates to a hydraulic anti-skid system for installation in a vehicle braking circuit between a master cylinder and a wheel brake cylinder to prevent the road wheels from locking in braking operation, and more particularly to a regulator valve arranged to control a hydraulic power pressure applied to an anti-skid apparatus from a hydraulic power pressure source in response to a master cylinder pressure.
2. Discussion of the Background
Such a conventional hydraulic anti-skid apparatus as described above includes a brake pressure control piston disposed within a hydraulic braking circuit between a master cylinder and wheel brake cylinders to increase or decrease the capacity of the braking circuit in response to axial displacement of the piston, a cut-off valve disposed within the braking circuit to be closed in response to the axial displacement of the piston, a hydraulic power pressure source in the form of a fluid pump driven by a prime mover of the vehicle to apply a hydraulic power pressure to the piston, a regulator valve arranged to control the hydraulic power pressure in accordance with a master cylinder pressure from the master cylinder, and an electrically operated valve arranged to be energized in accordance with a skidding condition of the vehicle to control the power pressure applied to the piston.
In the above arrangement, the regulator valve comprises a regulator piston arranged to be applied at opposite ends thereof with the master cylinder pressure and the power pressure, and a valve seat element arranged to cooperate with a valve part of the piston so as to control the power pressure in response to axial displacement of the regulator piston. If in operation the brake pressure control piston is axially displaced to a large extent when the regulator piston is being applied with the master cylinder, there will occur a sudden change of the power pressure. This causes pulsation of the power pressure and vibration of the regulator piston, resulting in unpleasant noises being generated in the brake system.